Mac OS X Panther in a Nutshell, 2nd Edition

Java on the Command Line

You can run Java programs from the command line using the java command. Generally, you invoke it in one of two ways:

java [options] [class] argument1 argument2...

Loads the specified class, and runs its main method. If it has no such method, or if it’s in the wrong format, the class will fail to launch. To be invokable like this, a Java class’s main method must have the signature:

public static void main(String[] args).

You should have a class path defined so that the Java interpreter will know where on the filesystem to search for the specified class. See the next section.

java [options] -jar jarfile arguments

In this case, the -jar option tells the Java interpreter to launch a program encapsulated in a jar file. This works only if the jar file knows its own Main-class, which defines the main method.

jar files, like Mac OS X applications, are self-contained and ignore the user’s class path definitions.

This section involves using the Terminal. If you are completely unfamiliar with this application or with using a Unix command line in general, you may want to skip ahead to Chapter 18 first.

You can find a full list of Java’s options under its manpage, but here are some of the more useful ones:

-cp

Lets you define the class path for one command invocation. See the next section.

- property = value

Sets a system property value.

-verbose

Displays information about each loaded class.

Tip

If the Java program you want to run from the command line is a self-contained ...